Thermosiphon system for hot water heater

ABSTRACT

A thermosiphon system for hot water heaters. In an embodiment, the thermosiphon includes a multi-tubular structure which in an embodiment is insertable through the cold water connection in a hot water tank in order to provide for a thermosiphon action in the hot water heater, to keep water circulating and prevent temperature stratification of water in the tank. In another embodiment, a thermosiphon design is fabricated within a water heater tank at the factory.

RELATED PATENT APPLICATIONS

This application is a divisional and claims priority under 35 USC § 121of prior and now pending U.S. patent application Ser. No. 15/346,071filed Nov. 8, 2016, which application claimed priority under 35 USC §119(e) from U.S. Provisional Patent Application Ser. No. 62/351,469,filed Jun. 16, 2016 and U.S. Provisional Patent Application Ser. No.62/271,093, filed Dec. 22, 2015 entitled THERMOSIPHON SYSTEM FOR HOTWATER HEATER, the disclosures of each are incorporated herein in theirentirety, including the specification drawing, and claims, by thisreference.

STATEMENT OF GOVERNMENT INTEREST

Not Applicable.

COPYRIGHT RIGHTS IN THE DRAWING

A portion of the disclosure of this patent document contains materialthat is subject to copyright protection. The patent owner has noobjection to the facsimile reproduction by anyone of the patent documentor the patent disclosure, as it appears in the Patent and TrademarkOffice patent file or records, but otherwise reserves all copyrightrights whatsoever.

TECHNICAL FIELD

This disclosure relates to hot water heaters, particularly thosedesigned and sized for residential or light commercial use, and toimproving energy efficiency and to reducing biological contamination insuch water heaters.

BACKGROUND

A continuing need exists for improvements in residential hot watersystems, in order to reduce energy usage. Also, it would be advantageousif biological growth experienced in such systems were substantiallyreduced or eliminated. Further, it would be advantages if suchimprovements were available either in a “built-in” form and integrallyprovided with a new water heater, or in an “add-on” form, suitable foreither retrofit or in combination with a new water heater.

Further, although I have previously disclosed various attempts at suchimprovements, by continuing to work in the field, I have discovered thatfurther refinement of the basic concept of use of thermosiphons in waterheaters would be yet further advantageous. In U.S. Pat. No. 4,777,347,issued to B. J. Mottershead on Oct. 11, 1988, and entitled ElectricWater Heating Tank with Thermosiphonic Circulation for Improved HeatRecovery Rate, I disclosed the concept of the use of a liquid loopexternal to a water heater tank as being helpful in improving the heatrecovery rate in hot water heaters. In U.S. Pat. No. 6,370,328 B1,issued to B. J. Mottershead on Apr. 9, 2002, and entitled Water HeatingTank with Thermosiphonic Circulation for Improved Heat Recovery Rate, Idisclosed the concept of the use of an internal liquid loop circulationpipe in a water heater tank, coupled with a check valve between the hotwater outlet and the cold water inlet, as being helpful in improving theheat recovery rate in hot water heaters. The disclosures of each ofthose prior United States patents are incorporated herein in theirentirety by this reference.

A common problem encountered with my prior art devices when use wasattempted in various new or retrofit construction settings is that theconcepts required apparatus not normally provided either as an integralcomponent of a hot water heater, or as a readily available and easilyinstallable add-on component to a hot water tank installation. Thus,such prior art hot water tank thermosiphonic circulation devicesinevitably present difficulty to plumbers or to the general public withrespect to implementing an improved, more efficient hot water system.

Thus, there remains a continuing unmet need for (a) a hot water tankdesign which includes, factory build in a tank, a reliable thermosiphonconfiguration, and alternately, (b) a thermosiphon apparatus designwhich is easily can be easily retrofitted to existing hot water heaters,or added at time of construction to new hot water tank installations.

SOME OBJECTS, ADVANTAGES, AND NOVEL FEATURES

Accordingly, one objective of my invention is to provide a design for athermosiphon which is simple, straightforward, and which is sized andshape for addition to existing hot water heaters.

Another objective of my invention is to provide a design for athermosiphon which may be easily installed in new hot water tanksystems.

Another important objective is to provide a hot water heater in which areliable thermosiphon is built into the hot water heater at the factory,so that the hot water heater always enjoys the benefit of higher heatrecovery rate, higher efficiency.

A related and important objective is to provide a hot water heaterdesign which in normal use minimizes or eliminates biologicalcontamination.

A related and important objective is to provide a retrofitablethermosiphon design which includes a multi-tubular structure that issized and shaped so that it can be easily inserted into a hot water tankutilizing industry standard cold water inlet plumbing connections.

Another important objective is to provide an easily assembledthermosiphon kit that can be easily installed by competent andexperienced plumbers in existing residential hot water systems.

Finally, another important objective is to provide a high qualitythermosiphon system design which can be conveniently and easily builtwith conventional manufacturing processes, so that manufacturing costsare minimized.

SUMMARY

I have now invented an improved thermosiphon system for use with hotwater heaters, and in particular, for hot water heaters configured forresidential or light commercial water heating service. Theseimprovements are important since they improve energy efficiency in hotwater heaters and improve their heat recovery rate. Also, continuousrecirculation of water in a hot water tank by way of an internalthermosiphon, or an external thermosiphon, as taught herein, isimportant since it effectively eliminates temperature stratification inhot water heaters, especially as may occur during periods of low ornon-use of hot water, and thus minimizes or effectively eliminates theoccurrence of biological growth in inside the tanks of hot waterheaters.

One embodiment of my thermosiphon system is for use internal to the tankof a hot water heater. The combination of a water heater and an internalthermosiphon includes a tank with sidewalls defining an internal spaceof height H between a bottom portion and a top portion, and athermosiphon. The hot water heater tank is adapted to be normally filledwith water to be heated. The tank includes a cold water inlet in the topportion, and a hot water outlet in the top portion. The thermosiphon maybe provided with components including a multi-tubular structure disposedalong a longitudinal axis internal to the tank. Such internalthermosiphon designs may utilize a cold water tube extending between anupstream end and a downstream end, with the upstream end fluidlyconnected to the cold water inlet in the top portion of the tank, andwith the downstream end open and adapted for discharge of watertherefrom. Such an internal thermosiphon design may also include a hotwater tube which is spaced outwardly from and situated longitudinallyalong at least a portion of the cold water tube. Such a hot water tubemay extend between a hot water inlet end having a hot water inlet, and ahot water output end which is open and adapted for discharge of watertherefrom. The hot water tube may further include an inlet capsubstantially sealed to the cold water tube at a location adjacent tothe cold water inlet. In an embodiment, the multi-tubular structure inthe thermosiphon may be provided in the form of a pair of concentrictubes nested about the longitudinal axis, so that the cold water tubeprovides a centrally located cold water passageway, and wherein the hotwater tube is spaced outwardly from the cold water tube, so that anannular hot water passageway is provided between the cold water tube andthe hot water tube. Such a thermosiphon design may further include a hotwater collection tee within the tank, where the hot water collection teehas a tee inlet, a first outlet fluidly connected to the hot wateroutlet in the top portion of the tank, and a second outlet fluidlyconnected to the hot water inlet of the multi-tubular structure. Invarious internal thermosiphon embodiments, the multi-tubular structuremay have a length L_(I) inside the tank and along the longitudinal axiswhich is up to seventy five percent (75%) of the internal height Havailable within the tank.

Another embodiment of my thermosiphon system is configured for useexternal to the tank of a hot water heater. Typical water heaters forresidential or light commercial use may have a tank with internalsidewalls defining an internal space of height H. Such tanks are adaptedto be normally filled with water for heating of the water. Based onvarious local, state, or national plumbing or building coderequirements, the tanks have a top portion with (1) a cold water inletof internal diameter D_(C) and (2) a hot water outlet. In many codecompliant designs, the cold water inlet and hot water outlet may beprovided using a male pipe fitting welded or otherwise secured to thetank at one end, and having ¾ inch NPT (National Pipe Thread Taper)threads ready for use with conventional pipe fittings.

In any event, a thermosiphon having a multi-tubular structure disposedalong a longitudinal axis may be provided for insertion through the coldwater inlet of hot water tank. In such a configuration, themulti-tubular structure may have an overall diameter D_(T), which isless than the internal diameter D_(C) of the cold water inlet, so thatthe multi-tubular structure is insertable through the cold water inletand thus into the tank. The multi-tubular structure may include a hotwater tube extending between a siphon inlet and a siphon exit. Thesiphon exit adapted for discharge of water therefrom. In such design, acold water tube may be provided spaced outwardly from and situatedlongitudinally along at least a portion of the hot water tube. The coldwater tube extends between a cold water inlet end having a cold waterinlet, and a cold water output end which is open and adapted fordischarge of water therefrom. The apparatus further includes an externalhot water T, which has a hot water T inlet fluidly attachable to the hotwater outlet in the tank for receiving hot water therefrom, and a hotwater T outlet for discharge of hot water to be used outward therefrom,and a hot water T siphon outlet, for providing hot water to the hotwater tube of the multi-tubular structure. At the juncture of the hotwater T siphon outlet and the cold water inlet tube to the multi-tubularstructure, a transition tube is provided. The transition tube has a hotwater inlet configured to receive a supply of hot water from the hotwater T siphon outlet and direct the supply of hot water to the hotwater tube.

In an embodiment, the transition tube may include (1) an inlet flangefluidly sealed with respect to the hot water T siphon outlet (at theoutside of the flange) and to the transition tube (at the inside of theflange). A bend portion is provided to change the direction of a hotwater stream to connect with the hot water tube. A transition tubeoutlet is provided. The transition tube outlet has sidewalls defining ahot water receiving passageway for receiving hot water from the hotwater T siphon outlet and delivering hot water to the hot water tube. Inan embodiment, the multi-tubular structure includes a pair of concentrictubes nested about said longitudinal axis, wherein the hot water tubeprovides a centrally located hot water passageway, and wherein a coldwater tube is spaced outwardly from the hot water tube, to provideannular cold water passageway between an outer wall of the hot watertube and an inner wall of the cold water tube. In various embodiments,the multi-tubular structure of the thermosiphon may have a length L_(I)that is inserted inside the tank where the length L_(I) is greater thanabout 75% of the inside height H of the tank.

BRIEF DESCRIPTION OF THE DRAWING

The present invention(s) will be described by way of exemplaryembodiments, using for illustration the accompanying drawing in whichlike reference numerals denote like elements, and in which:

FIG. 1 is a perspective of for an embodiment in which a thermosiphon isprovided within a hot water tank.

FIG. 2 is a conceptual vertical cross sectional view of an embodimentsuch as just illustrated in FIG. 1, where a thermosiphon is providedinside a hot water tank; those of skill in the art need not be providedwith detailed mechanical details such as might be useful in assembly ofthreaded pipe or fabrication by brazing or welding components asillustrated in this or other figures of the drawing.

FIG. 2A is an end view, of a multi-tubular thermosiphon, taken lookingup at the location 2A-2A as indicated in FIG. 2.

FIG. 3 is a perspective of for an embodiment in which a thermosiphon isprovided separately and externally from a hot water tank; however, itshould be appreciated that the multi-tubular structure component of thethermosiphon is configured for insertion though the cold water inlet tothe tank, and extends downward into the tank upon assembly.

FIG. 3A is an end view, of an insertable multi-tubular thermosiphon,taken looking up at the location 3A-3A as indicated in FIG. 4.

FIG. 4 is a conceptual vertical cross sectional view of an embodimentsuch as just illustrated in FIG. 3, where a thermosiphon is provided forexternal insertion into a hot water tank.

FIG. 5 is front perspective, partial cross-sectional view of atransition tube, showing a portion of the hot water T siphon outlet, aninlet flange fluidly sealed at the outer rim thereof to the inside ofthe hot water T siphon outlet, and fluidly sealed at the inner rimthereof to the outside of the inlet of the transition tube, as well asshowing the bend portion which directs hot water to the hot water tube.

FIG. 6 is rear perspective, partial cross-sectional view of a transitiontube, showing a portion of the hot water T siphon outlet, an inletflange fluidly sealed at the outer rim thereof to the inside of the hotwater T siphon outlet, and the inlet flange fluidly sealed at the innerrim thereof to the outside of the inlet of the transition tube, as wellas showing the bend portion which directs hot water to the hot watertube.

The foregoing figures, being merely exemplary, contain various elementsthat may be present or omitted from a final configuration for anembodiment of a thermosiphon system for use with a hot water heater, orthat may be implemented in various embodiments described herein for useeither internally to, or assembled externally for use with, a hot waterheater. Other variations in thermosiphon systems for hot water heatersmay use slightly different mechanical structures, mechanicalarrangements, or size and shape of components, and yet employ theprinciples described herein and as generally depicted in the drawingfigures provided, and as more specifically called out in the claims setforth below. An attempt has been made to draw the figures in a way thatillustrates at least those elements that are significant for anunderstanding of an exemplary thermosiphon system for use with hot waterheaters, and suggestive embodiments for different approaches to usingthermosiphonic devices with hot water heaters.

It should be understood that various features may be utilized in accordwith the teachings hereof, as may be useful in different embodiments asuseful for various sizes and shapes of thermosiphon structures for hotwater heaters, depending upon the specific requirements (such as typicalheight of a hot water heater tank) within the scope and coverage of theteachings herein as defined by the claims. Further, like features invarious embodiments for thermosiphon system designs may be describedusing like reference numerals, or other like references, without furthermention thereof.

DETAILED DESCRIPTION

Attention is directed to FIG. 1, where a water heater 10 having aninternal thermosiphon is illustrated. In an embodiment, the provision ofthese elements, factory built, is an important improvement in the art.Hot water heater 10 includes a tank 12 with internal sidewalls 14defining an internal space of height H (see FIG. 2) between a bottomportion 16 and a top portion 18. The hot water tank 10 adapted to benormally filled with water, which is not separately illustrated.However, generally, arrows representing cold water are shown with arrowshaving tails with solid lines—see reference CW in FIG. 2. Likewise,arrows representing hot water are shown with arrows having tails withbroken lines—see reference HW in FIG. 2. The tank 12 includes cold waterinlet 20 in the top portion 18. A hot water outlet 22 is provided in thetop portion.

A thermosiphon 30 system is provided within tank 12. The thermosiphonsystem includes multi-tubular structure 32 and a hot water collectiontee 34. The hot water collection tee 34 has a tee inlet 62, a firstoutlet 64 fluidly connected to the hot water outlet 22 in said topportion 18, and a second outlet 66 fluidly connected to a hot waterinlet 42 on the multi-tubular structure 32.

In an embodiment, a multi-tubular structure 32 may be located internalto the tank 12 and disposed along a longitudinal axis which isidentified in FIG. 1 as centerline of axis A. In an embodiment thelongitudinal axis of multi-tubular structure 32 may be parallel to thevertical axis of the water heater 10 (usually the same as verticalsidewalls of tank 12) in which the multi-tubular structure 32 isfabricated. The multi-tubular structure 32 of the thermosiphon 30includes a cold water tube 40 extending between an upstream end 42 and adownstream end 44. The upstream end 42 is fluidly connected to the coldwater inlet 20 in the top portion 18. The downstream end 44 is open (seeFIGS. 2 and 2A) and adapted for discharge of cold water 46. A hot watertube 50 is provided. The hot water tube 50 is spaced outwardly from andsituated longitudinally along at least a portion of the cold water tube40. The hot water tube 50 extends between a hot water inlet end 52having a hot water inlet 54, and a hot water output end 56 which is openand adapted for discharge of hot water 57 therefrom. The hot water tube50 may further include an inlet cap 58 substantially sealed to the coldwater tube 40 adjacent the cold water inlet 20.

As better seen in FIG. 2A, the multi-tubular structure 32 may befabricated in the form of a pair of concentric tubes nested about thelongitudinal axis A. In an embodiment as shown in FIGS. 1, 2, and 2A,the cold water tube 40 provides a centrally located cold waterpassageway 41. In such embodiment, the hot water tube 50 is spacedoutwardly from the cold water tube 40, thus providing an annular hotwater passageway 60 between the cold water tube 40 and the hot watertube 50.

In an embodiment, the hot water collection tee 34 is also located withinthe tank 12 of water heater 10. The hot water collection tee 34 includesa tee inlet 62, a first outlet 64 fluidly connected to the hot wateroutlet 22 in the top portion 18, and a second outlet 66 fluidlyconnected through orifice 68 which may be provided in an annular diskconfiguration having an outer radius (R) and an inner radius (r) so thatit also serves as an orifice through which how water HW enters the hotwater inlet 54 in the hot water tube 50.

In various embodiments, the multi-tubular structure 32 has a lengthL_(I) inside the tank 12 (see FIG. 2) along the longitudinal axis A, andthe length L_(I) is greater than fifty percent (50%) of the insideheight H of tank 12.

In various embodiments, the multi-tubular structure 32 has a lengthL_(I) inside the tank 12 (see FIG. 2) along the longitudinal axis A, andthe length L_(I) is greater than seventy-five percent (75%) of theinside height H of tank 12.

In various embodiments, the multi-tubular structure 32 has a lengthL_(I) inside the tank 12 (see FIG. 2) along the longitudinal axis A, andthe length L_(I) is greater than ninety percent (90%) of the insideheight H of tank 12.

In various embodiments, the tank 12 may be provided as a cylindricaltank having an internal diameter D, and wherein height H is greater thandiameter D.

Attention is now directed to FIGS. 3, 3A, 4, 5, and 6, where anotherembodiment for a thermosiphon 130 is illustrated. A thermosiphon 130includes a multi-tubular structure 132 sized and shaped for use incombination with a residential water heater 110 having a tank 112 withinternal sidewalls 114 defining an internal space of height H. The tank112 is adapted to be normally filled with water for heating of thewater. The tank 112 has a top portion 118 with a cold water inlet 120 ofinternal diameter D_(C) and a hot water outlet 122.

The thermosiphon includes a multi-tubular structure 132 and an externalhot water T 134. The multi-tubular structure 132 may be disposed along alongitudinal axis B and have an overall diameter D_(T). In order to sizeand shape the multi-tubular structure 132 so that the multi-tubularstructure 132 is insertable through the cold water inlet 120 and thenceinto the tank 112, the multi-tubular structure 132 must have a diameterD_(T) less than the inside diameter D_(C) of the cold water inlet 120,as illustrated in FIG. 3A.

The multi-tubular structure 132 includes a hot water tube 150 extendingbetween a siphon inlet 152 and a siphon exit 154. The siphon exit 154adapted for discharge of hot water 157 therefrom. The multi-tubularstructure also includes a cold water tube 140. The cold water tube 140is spaced outwardly from and situated longitudinally along at least aportion of the hot water tube 150. The cold water tube 140 extendsbetween a cold water inlet end 142 having a cold water inlet 143, and acold water output end 144 which is open and adapted for discharge ofcold water 145 therefrom.

An external hot water T 134 is provided for hot water HW return from thetank 112 to the multi-tubular structure 132 of thermosiphon 130. Theexternal hot water T 134 includes a hot water T inlet 162 fluidlyattachable to the hot water outlet 122 in the tank 112, a hot water Toutlet 164, and a hot water T siphon outlet 166.

For returning hot water HW to the multi-tubular structure 132, atransition tube 170 is provided. To accommodate the transition tube 170,an enlarged cold water tube portion 141 may be provided, and enlargedcold water tube portion 141 may have a larger outside diameter than coldwater tube 140. The transition tube 170 having a hot water inlet 172configured to receive a supply of hot water HW from the hot water Tsiphon outlet 166 and direct the supply of hot water HW to the hot watertube 150. The transition tube 170 includes (1) an inlet flange 173 whichmay be provided in an annular disk configuration having an outer radius(R) and an inner radius (r) so that it also serves as an orifice and maybe fluidly sealed with respect to the hot water T siphon outlet 166, (2)a bend portion 174, and (3) a transition tube outlet 176. The transitiontube 170 has interior sidewalls 178 defining a hot water receivingpassageway 180 for receiving hot water HW from the hot water T siphonoutlet 166 and delivering the hot water HW to the hot water tube 150.

As seen in FIGS. 3A and 4, in an embodiment, the multi-tubular structure132 may be provided as a pair of concentric tubes (140 and 150) nestedabout the longitudinal axis B. In this embodiment, the hot water tube150 provides a centrally located hot water passageway 156. The coldwater tube 140 is spaced outwardly from the hot water tube 150 andprovides an annular cold water passageway 181 between an outer wall 182of the hot water tube 150 and an inner wall 184 of the cold water tube140, from which cold water 145 is discharged.

In various embodiments, the multi-tubular structure 132 has a lengthL_(I) inside the tank 112 (same parameters as shown in FIG. 2 apply)along the longitudinal axis B, and the length L_(I) is greater than 50%of the inside height H of tank 112.

In various embodiments, the multi-tubular structure 132 has a lengthL_(I) inside the tank 112 (same parameters as shown in FIG. 2 apply)along the longitudinal axis B, and the length L_(I) is greater than 75%of the inside height H of tank 112.

In various embodiments, the multi-tubular structure 132 has a lengthL_(I) inside the tank 112 (same parameters as shown in FIG. 2 apply)along the longitudinal axis A, and the length L_(I) is greater than 90%of the inside height H of tank 12.

In various embodiments, the tank 112 may be provided as a cylindricaltank having an internal diameter D, and wherein height H is greater thandiameter D.

In order to evaluate and confirm the advantages of a water heater designwhich incorporates a thermosiphon as taught herein, comparative testingwas conducted at an accredited testing laboratory which is approved forUnited States Environmental Protection Agency Energy Star Testing. Two(2) water heaters were tested, each having a nominal fifty (50) gallonsize, one water heater without, and one water heater with an internalthermosiphon as taught herein. All tests were conducted in accord withthe procedures set out in the United States Code of Federal Regulations,as found at 10 C.F.R. Chapter II, Part. 430, Subpart B, Appendix E,entitled Uniform Test Method for Measuring Consumption of Water Heaters,which test procedures are incorporated herein in their entirety by thisreference, as they existed on Mar. 22, 2016. A modified water heaterhaving an internal thermosiphon as taught herein was tested, A modifiedfifty (50) gallon hot water heater, was provided for testing, BradfordWhite Model RE 350T1, Serial No. ME36250436. An unmodified hot waterheater by the same manufacturer, Bradford White Model RE350T6, havingSerial Number ME36218123 was also tested. Bradford White Corporation isa well-known manufacturer of hot water heaters, with corporateheadquarters at 725 Talamore Drive, Ambler, Pa., 19002, United States ofAmerica. See http://www.bradfordwhite.com/ for more information.

The full test results for the unmodified water heater are set out inAppendix A. Comparative test results are set out in Table 1 below.

The full test results for a modified water heater using an internalthermosiphon system as taught herein are set out in Appendix B.Comparative test results are set out in Table 1 below.

TABLE 1 COMPARATIVE TEST RESULTS Modified Unmodified Item Water HeaterWater Heater Remarks Tank Storage 45.0 gallons 45.0 gallons Volume¹First Hour Rating 79.6 gallons 52.9 gallons 26.7 gallons increaseRecovery 0.98 0.98 Allowed by Efficiency 10CFR Ch. II, 430(e) DailyEnergy Use 42,196 BTUs 44,892 BTUs 2696 BTUs savings Annual Energy15,402 BTU/yr 16,544 BTU/yr 335 kWh/yr savings Use or or 4,514 kWh/yr4,849 kWh/yr Energy Factor 0.983 0.913 Δ = 0.07 ¹Storage Tank watertemperature was thermostatically maintained at 135° F. plus or minus 5°F.

The test results set out in Table 1 speak for themselves when viewed byone of ordinary skill in the art and to whom this specification isdirected. It is clear that in otherwise identical water heaters ofnominal fifty (50) gallon capacity, the use of a modified water heateras taught herein would save a homeowner 335 kilowatt hours per year inenergy costs. While the savings may be modest to the individualhomeowner (for example about US$28.47 per year if the cost ofelectricity is 8.5 cents per kwH), such savings would be appreciable ifsuch devices were installed in homes of large segments of thepopulation. As an individual water heater of the same size produces morehot water (a 26.7 gallon increase in the First Hour Rating) while usingless energy, the advantages provided by way of use of the inventiveinternal thermosiphon hot water heater becomes quite clear. Further,since energy savings based on hot water usage as projected by the testcriteria noted above amounts to some 335 kilowatt hours per year per hotwater heater, each installed hot water heater using the inventiveapparatus disclosed herein would save 0.335 megawatt of energy usageover a year. In more basic terms, the use of a hot water heater withinternal thermosiphon as disclosed herein by approximately 2400 homeswould save about 800 megawatts per year of power. Such energy savingscould significantly contribute to reducing new energy generationcapacity required to serve a growing population. Where fossil fuels suchas natural gas, oil, or coal are used for electrical power generation,such electricity savings as would be achievable by widespread use of theinventive internal thermosiphon hot water heater as disclosed hereinwould contribute to considerable greenhouse gas generationreduction—simply by using more efficient hot water heaters.

Additionally, by using an embodiment of a thermosiphon in a hot waterheater in accord with the teachings herein, biological growth in aresidential hot water supply tank may be controlled or substantiallyeliminated. Such a method may be practiced by providing a hot water tankas set forth herein, then providing water to the hot water tank, andheating water in the hot water tank through conventional hot waterheating equipment as may be normally supplied to residential hot waterheaters. However, additionally, by circulating water in the hot watertank using a thermosiphon as set forth in one of the embodimentsdescribed herein, I have found that it is possible to substantiallyprevent vertical temperature stratification of water within a hot watertank. Consequently, by way of maintaining the temperature of the waterin said tank above a selected temperature that inhibits or killsbacteria, it has been found that bacterial contamination is reduced orsubstantially eliminated. In an embodiment, setting the hot watertemperature at about at about 180° F. may accomplish such a goal.

It is to be appreciated that my thermosiphonic systems for hot waterheaters is an appreciable improvement in the art of energy efficient hotwater heaters. My novel design addresses the problem of how to providefor either a “factory built” hot water tank including a thermosiphon forcontinuous recirculation of water in the tank, or a “field built”thermosiphon design for use with a conventional factory built hot watertank which has not been provided with a thermosiphon system builttherein.

Although only a few exemplary embodiments have been described in detail,various details are sufficiently set forth in the drawings and in thespecification provided herein to enable one of ordinary skill in the artto make and use the invention(s), which need not be further described byadditional writing in this detailed description. It will be readilyapparent to those skilled in the art that my thermosiphon system for hotwater tanks may be modified from those embodiments provided herein,without materially departing from the novel teachings and advantagesprovided.

The aspects and embodiments described and claimed herein may be modifiedfrom those shown without materially departing from the novel teachingsand advantages provided by this invention, and may be embodied in otherspecific forms without departing from the spirit or essentialcharacteristics thereof. Therefore, the embodiments presented herein areto be considered in all respects as illustrative and not restrictive. Assuch, this disclosure is intended to cover the structures describedherein and not only structural equivalents thereof, but also equivalentstructures. Numerous modifications and variations are possible in lightof the above teachings. It is therefore to be understood that within thescope of the appended claims, the invention(s) may be practicedotherwise than as specifically described herein. Thus, the scope of theinvention(s), as set forth in the appended claims, and as indicated bythe drawing and by the foregoing description, is intended to includevariations from the embodiments provided which are neverthelessdescribed by the broad interpretation and range properly afforded to theplain meaning of the claims set forth below.

1. A thermosiphon sized and shaped for use in combination with aresidential water heater having a tank with internal sidewalls definingan internal space of height H, the tank adapted to be normally filledwith water for heating of the water, the tank having a top portion with(1) a cold water inlet of internal diameter D_(C) and (2) a hot wateroutlet, said thermosiphon comprising: a multi-tubular structure disposedalong a longitudinal axis and having an overall diameter D_(T), saiddiameter D_(T) less than said diameter D_(C), so that said multi-tubularstructure is insertable through said cold water inlet into said tank,said multi-tubular structure including (a) a hot water tube extendingbetween a siphon inlet and a siphon exit, said siphon exit adapted fordischarge of water therefrom, and (b) a cold water tube, said cold watertube spaced outwardly from and situated longitudinally along at least aportion of said hot water tube, said cold water tube extending between acold water inlet end having a cold water inlet, and a cold water outputend which is open and adapted for discharge of water therefrom; anexternal hot water T, said external hot water T having a hot water Tinlet fluidly attachable to said hot water outlet in said tank, a hotwater T outlet, and a hot water T siphon outlet; a transition tube, saidtransition tube having a hot water inlet configured to receive a supplyof hot water from said hot water T siphon outlet and direct the supplyof hot water to said hot water tube, said transition tube comprising (1)an inlet flange fluidly sealed with respect to said hot water T siphonoutlet, (2) a bend portion, and (3) a transition tube outlet, saidtransition tube having interior sidewalls defining a hot water receivingpassageway for receiving hot water from said hot water T siphon outletand delivering hot water to said hot water tube; and wherein saidmulti-tubular structure comprises a pair of concentric tubes nestedabout said longitudinal axis, wherein said hot water tube provides acentrally located hot water passageway, and wherein said cold water tubeis spaced outwardly from said hot water tube and provides an annularcold water passageway between an outer wall of said hot water tube andan inner wall of said cold water tube.
 2. The thermosiphon as set forthin claim 1, wherein said multi-tubular structure has a length L_(I)inside said tank and along said longitudinal axis, and wherein saidlength L_(I) is greater than 50% of said height H.
 3. The thermosiphonas set forth in claim 1, wherein said multi-tubular structure has alength L_(I) inside said tank and along said longitudinal axis, andwherein said length L_(I) is greater than 75% of said height H.
 4. Thethermosiphon as set forth in claim 1, wherein said multi-tubularstructure has a length L_(I) inside said tank and along saidlongitudinal axis, and wherein said length L_(I) is greater than 90% ofsaid height H.
 5. A method for controlling biological growth in aresidential hot water supply tank, said method comprising: (a) providinga hot water tank, said hot, water tank comprising a tank with sidewallsdefining an internal space of height H between a bottom portion and atop portion, the tank adapted to be filled with water, the tankcomprising a cold water inlet in the top portion and a hot water outletin the top portion; a thermosiphon, said thermosiphon located withinsaid tank and including a multi-tubular structure disposed along alongitudinal axis, said thermosiphon having (a) a cold water tubeextending between an upstream end and a downstream end, said upstreamend fluidly connected to said cold water inlet in said top portion, andsaid downstream end adapted for discharge of water therefrom within saidwater heater, and (b) a hot water tube, said hot water tube spacedoutwardly from and situated longitudinally along at least a portion ofsaid cold water tube, said hot water tube extending between a hot waterinlet end having a hot water inlet, and a hot water output end which isopen and adapted for discharge of water therefrom, said hot water tubefurther comprising an inlet cap substantially sealed to said cold watertube adjacent said cold water inlet, wherein said multi-tubularstructure comprises a pair of concentric tubes nested about saidlongitudinal axis, wherein said cold water tube provides a centrallylocated cold water passageway, and wherein said hot water tube is spacedoutwardly from said cold water tube and provides an annular hot waterpassageway between said cold water tube and said hot water tube; a hotwater collection tee within said tank, said hot water collection teeincluding a tee inlet, a first outlet fluidly connected to said hotwater outlet in said top portion, and a second outlet fluidly connectedto said hot water inlet of said thermosiphon; and wherein saidmulti-tubular structure has a length L_(I) inside said tank and alongsaid longitudinal axis, and wherein said length L_(I) is greater than75% of said height H; (b) providing water to said hot water tank; (c)heating water in said hot water tank; circulating water in said hotwater tank with said thermosiphon, to thereby substantially preventvertical temperature stratification of water within said hot water tank;and (d) maintaining the temperature of the water in said tank at about180° F., or more.
 6. The method as set forth in claim 5, wherein saidhot water tank comprises a generally cylindrical tank having an internaldiameter D, and wherein height H is greater than diameter D.
 7. A methodfor controlling biological growth in a hot water tank, said methodcomprising: providing a hot water tank; providing a thermosiphon as setforth in claim 1; providing water to said hot water tank; heating waterin said hot water tank; circulating water in said hot water tank withsaid thermosiphon to thereby substantially prevent vertical temperaturestratification of water within said hot water tank; and maintaining thetemperature of the water in said tank at about 180° F., or more.
 8. Themethod as set forth in claim 7, wherein said hot water tank comprises agenerally cylindrical tank having an internal diameter D, and whereinheight H is greater than diameter D.